This invention relates to a composition for use in reducing noise and/or fouling in a liquid cooling system of an engine, and a method of reducing noise and/or fouling in such a liquid cooling system.
It is known that noise is produced as a result of vortexing cavitation, and eddying when liquid flows in pipes, ducts, and hollow castings.
The methods currently used to reduce noise produced by liquid flowing in closed systems specifically the cooling system of a heat engine, has to date been concentrated on macro-mechanical aspects, i.e. by varying the pump specification or surrounding the sound source in sound absorbing materials, or increasing the thickness of the liquid container. Other methods have been to reduce the cooling system volume to a minimum or to polish the internal surfaces of the coolant conducting pipes whose normal bend, constrictions, expansions, and roughness promote the vortexing cavitation, and eddying that produces vibrations and noise.
All these methods have limited application, and fail to resolve the primary causes of the noise, i.e. cavitation. vortexing, and eddying produced as the liquid circulates.
An object of the present invention is to provide a composition and a method of reducing (the primary causes of noise at a xe2x80x9cmicro-mechanicalxe2x80x9d level resulting in reduced cavitation, vortexing, and eddying, and therefore noise.
A first aspect of the invention provides a composition for use in reducing noise fouling in a liquid cooling system of an engine comprising an organo-polymeric microfibril material insoluble in the cooling liquid of the liquid cooling system, the microfibrils having an aspect ratio (length to diameter) in the range 10 to 5000.
A second aspect of the invention provides a method of reducing noise and/or fouling, in a liquid cooling system of an engine comprising adding the composition according, to the first aspect of the invention to a liquid cooling system of an engine.
The microfibril material when introduced into the liquid cooling system reduces cavitation, vortexing, eddying, and therefore noise. In addition it reduces the fouling, if any, of the internal surfaces of the cooling system.
Preferably the aspect ratio is in the range 10 to 3000. Excessive aspect ratio would lead to entanglement of individual microfibrils, and hence precipitation in the flowing, liquid.
Preferably, the organo-polymeric microfibril material is a solid organic polymer in the form of microfibrils having an average diameter in the range of 1 nm-15 xcexcm, an average length in the range of 100 nm-3 mm. Polymeric materials to be processed into microfibrils should be insoluble but highly dispersible in a given coding liquid. There may be used for example polyethylene, polyproplyene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polytetrafluoroethylene, polyethylene terephthalate, polymethylmethacrylate nylon, polycarbonate, and copolymers or blends thereof.
Polymeric compounds known for their heat resistance may be used which include para-amides, aromatic polyamides, aromatic polyethers, polyetheretherketones, aromatic polyesters, aromatic polyimides, and polybenzoimidazoles.
Polymeric materials that have been found particularly preferable are those which are capable Of forming a liquid crystal. Specific examples include aramide fibres such as poly-p-phenylene terephthalamide wet spun from sulfuric acid liquid crystal solutions, and polybenzobisthiazole wet spun from polyphosphoric acid liquid crystal solution.
By xe2x80x9cmicrofibrilxe2x80x9d is meant short lengths of fibre. The microfibrils are not microfibrillated.
By xe2x80x9chighly dispersiblexe2x80x9d is meant the state of the polymeric microfibrils which can be seen to form a uniform suspension after being vigorously mixed for a period of time.
The choice of polymeric microfibril material will depend upon the particular kind of cooling liquid in which the material is used; clearly, the material should not react chemically with the cooling liquid of the liquid cooling system, nor with the carrier liquid. Furthermore, the polymeric microfibril material should not be readily degradable, but should have a reasonable life in the cooling liquid.
What is meant by the microfibrils being xe2x80x9cinsolublexe2x80x9d in a liquid may be determined by an experiment in which 1 weight percent of polymeric microfibrils is added to the liquid, and stirred vigorously for five hours at a working temperature, followed by filtration, and drying whereupon the material is measured for weight reduction. If this reduction is less than 10 weight parent of the original weight then the microfibril material is regarded as insoluble.
There is no restriction placed on how to make the polymeric microfibril material.
In order to improve the dispersibility of the microfibril material in the cooling liquid, and to enhance the stability of the resulting suspension, the material may be treated with a suitable surfactant, or chemically modified, or physically treated.
A suitable surfactant is modified alcohol xe2x80x9cEthylan CPG660xe2x80x9d or xe2x80x9cMonolan 8000/E80xe2x80x9d of Ackros Chemicals Limited.
The cooling liquid of the liquid cooling system may be aqueous or non-aqueous, e.g. hydrofluroether, water, oils, a liquid hydrocarbon or any other suitable liquid coolant.
In order to reduce the risk of dust health hazard, the said material is preferably contained in a carrier, The carrier may be, e.g. a liquid, a gel or a compressed tablet soluble a dispersible in the said cooling liquid.
The carrier is preferably completely soluble in the cooling liquid. When the carrier is a liquid or a gel it should prevent settling of the polymeric microfibril material during storage, and promote accurate dosing during packaging, or in production line application requiring portioning of bulk quantities. Such a carrier could be magnesium aluminium silicate in suspension, propylene glycol, cellulose solution or any other suitable compound.
The method of the invention finds effective application where liquids are used in closed cooling systems particularly where noise pollution or fouling are negative factors of the system, as with automotive cooling, systems, and more generally where any heat engine with a liquid cooled system is employed.